Assert which slice of the results the index shows: the first and the last item of the page and the total, as its footer says ("1–100 of 120").
Examples
Then the index should show items 1 to 100 of 120
Then the index should show items 101 to 120 of 120
Then the index should show items 1 to 14 of 14
And the index should show items 1 to 50 of 75
Then the index should show items 51 to 75 of 75
Pattern
Then(/^the index should show items (\d+) to (\d+) of (\d+)$/, …)
Part of @webship-js/craft-cms-steps (github.com/webship/craft-cms-steps), a step pack for Webship-js 2.0.x.